Performance of Novel Rectangular Partially Bonded Steel Mesh–Reinforced Elastomeric Bearings for Seismic Isolation of Bridges

Abstract

Steel plates have traditionally been the reinforcement of choice for conventional elastomeric bridge bearings. In addition, these bearings are often employed under fixed boundary conditions (bonded application) as seismic isolators. The main objective of this study is to develop a new type of elastomeric bearing with improved lateral flexibility and superior seismic isolation efficiency. The new bearing is a partially bonded mesh-reinforced (MR) elastomeric bearing. MR bearings employ high-strength steel mesh reinforcement layers instead of steel-reinforcing plates. Additionally, the bearing is utilized in a partially bonded application; that is, only a limited region at the central portion of the bearing contact surfaces is bonded to the top and bottom supports. Given this specific boundary condition and the bending flexibility of the mesh reinforcement layers, the MR bearing experiences lateral rollover deformations under shear loads. During lateral rollover deformation, the upper and lower surfaces of the bearing partially roll off the contact supports. This experimental study compared the cyclic lateral responses of bonded plate-reinforced (PR) bearings (as reference bearings) and their partially bonded MR-bearing counterparts. The elastomer material properties and geometrical characteristics of the two bearing types were identical. The experimental results suggest that partially bonded MR bearings are feasible, perform more flexibly in the lateral direction, and exhibit greater energy-dissipation capability than PR bearings. This study focuses on a new type of elastomeric bridge-bearing isolator designed to be more flexible horizontally and better at absorbing the input energy of earthquakes. The new bearing isolator was constructed using laminated rubber material layers that were bonded to high-grade steel mesh reinforcement layers instead of conventional steel plates. The mesh reinforcement is rigid when stretched in a flat direction; however, it can bend easily. The bearing isolator was only partially bonded to its supports, which allowed it to deform more freely in the horizontal direction. During horizontal deformation, the upper and lower surfaces of the bearing partially roll off the contact supports. In this study, the new bearing type was compared with the conventional (steel plate reinforced) type, and it was found that the new bearing type is more effective at absorbing seismic excitations and can provide greater flexibility in the horizontal direction. This new bearing type is called a partially bonded mesh-reinforced elastomeric bearing.